The general objective is to study the neural mechanisms for generation of respiratory rhythm in the mammal, with special reference to phase-switching. The method used is to ascertain the time relations between different brain-stem respiratory neuron activities, and between brain-stem and motoneuron (e.g. phrenic) activities, as influenced by perturbations of afferent inputs. Specific projects: 1. Use of intracellular recording to evaluate inhibitory inputs to inspiratory (I) and expiratory (E) neurons, especially by application of cycle-triggered inflations. 2. Study of I-E switching and of the mechanisms of long time-constant actions of airway stretch receptor inputs, by manipulating the timing of afferent vagal electrical stimulation. 3. Study of E-I switching by evaluating activity changes immediately preceding I onset, particularly in ventrolateral medullary neurons, as affected by vagal, superior laryngeal, and rostral pontine inputs. 4. Study of shaping of patterns of airway motoneurons (hypoglossal and recurrent laryngeal), as distinguished from spinal motoneuron patterns, by manipulation of afferent inputs. 5. Study by crosscorrelation of connection betwen specific populations, e.g. projections of rostral to caudal medullary E neurons, projections of decrementing I neurons to rostral and caudal E neurons (simultaneous extra- and intracellular recordings). 6. Study of bilaterality and plasticity of rhythm generator subsystems by use of brain-stem sagittal splitting, with evaluation of effects by use of power spectral analysis; evaluation of species-dependent effects (cat vs. rabbit). 7. Study of interactions between different I neuron populations by analysis of high-frequency oscillations, as influenced by tonic and phasic inputs, with evaluation of effects by use of phase-response curves and power spectral analysis.